The invention relates to speed responsive systems and more particularly to speed responsive systems for vehicles whereby the vehicle may be kept at or about a predetermined speed.
Systems are known for automatically controlling a motor vehicle to run at a predetermined speed which is set by the driver. Once the speed has been selected and set by the driver, the system operates automatically to hold the vehicle at that speed, subject, of course, to the speed being within the capability of the vehicle having regard to the gradient of the road and similar factors.
It is also known in such systems to provide means for sensing various operating parameters of the vehicle so as to disable the speed control system automatically when one or more of these parameters changes in such a manner as to indicate that it is no longer safe or expedient to maintain the vehicle under automatic control of the speed control system. For example, it is known to disable a speed control system when the driver operates the brakes of the vehicle, such disabling being carried out, for example, by monitoring an electrical signal dependent on conditions in the brake lamp circuit of the vehicle.
An object of the invention is to provide an improved vehicle speed control system.
A more specific object of the invention is to provide a vehicle speed control system having improved means for disabling the system automatically in the event of certain conditions arising.